Enzymes and Enzymatic Reactions Flashcards
what are enzymes?
Biological Catalysts that increase the speed of a reaction without being changed or used up
what are enzymes made up of?
they are large proteins
how does the ‘lock and key’ hypothesis work?
1)the substrate collides with the active site of the enzyme and becomes attached
2)the active site has a complementary shape/unique shape that fits onto the substrate as enzymes usually only catalyse one specific reaction
3)the enzyme catalyses the breakdown of the substrate and the products are released from the active site
4)the enzyme molecule is unchanged after the reaction and can be reused
draw the lock and key model of enzyme action and compare to this diagram:
How does the induced model fit of enzyme action differ to the lock and key model?
In the induced model fit, the active site changes shape a little as the substrate binds on to it in order to get a tighter fit
what factors affect the rate of an enzyme catalysed reaction?
-pH
-temperature
how does changing temperature affect the rate of an enzyme catalysed reaction?
•A higher temperature increases the rate of the reaction
•All enzymes have an optimum temperature they work best at
•If the temperature is too hot, some of the bonds holding the enzyme together break denaturing the enzyme
what happens when an enzyme is denatured?
the shape of the enzyme’s active site changes so the substrate no longer fits
how does changing pH affect the rate of an enzyme catalysed reaction?
•all enzymes have an optimum pH they work best at
•the optimum is usually pH 7 but not always e.g. pepsin breaks down proteins in the stomach at optimum pH 2 as it is well suited to acidic conditions
•If the pH is too high or low it interferes with bonds holding the enzyme together, denaturing the enzyme
How could you investigate the effect of pH on enzyme activity?
1)put a drop of iodine into every well of a spotting tile
2)place a bunsen burner on a heat proof mat and a tripod gauze over it. Put a beaker of water on top of the tripod and heat the water untill 35•C keeping the the temperature constant throughout the experiment
3) add amylase solution using a syringe and the same amount of buffer solution with a pH of 5 to a boiling tube and put the tube into the beaker of water and and wait 5mins
6) use a different syringe to add 5cm^3 of starch solution to boiling tube
7) use continuous sampling to record how long it takes for amylase to break down starch by using a drop pipette to take a fresh sample from the boiling tube every 30secs and put a drop into a well
8) when iodine solution remains browny orange starch is no longer present
9)repeat experiment using different pH values to see the impact of pH on amylase
how do you calculate the rate of reaction?
rate of reaction=change/time
During an investigation of catalase, 24cm^3 of oxygen was released in 50seconds. calculate the rate of reaction.
24/50= 0.48cm^3 s^-1
what is the name of the molecule that binds at the active site?
substrate
what is the rate of reaction?
a measure of how something changes overtime
what pH does pepsin work best at in the stomach?
pepsin breaks down proteins in the stomach at optimum pH 2 as it is well suited to acidic conditions
